JPH0929508A - High tenacity surface-coated hard metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve hardness of a base body surface part, by causing a hard phase in the surface part to contain plate-shaped crystal tungsten carbide in which crystals are orientated. SOLUTION: A surface part at a depth of 5 to 30μm from a surface of a hard metal toward its interior does not contain any first hard phase or else has an impoverished first hard phase in comparison with the central part of the hard metal. A second hard phase in the surface part contains plate-shaped crystal tungsten carbide in which crystals are oriented. Tenacity is little improved by forming the surface part where depth from the surface is smaller than 5μm in this surface part and improvement effect of chipping resistance as a tool made of surface-coated hard metal is low, while plastic deformation resistance is lowered and abrasion resistance is worsened at the depths greater than 30μm. Plate-shaped crystals WC have aspect ratios of 3 to 20 observed in a cross-sectioned structure of a base body and amount to more than 30 volume % of a total of tungsten carbide contained in the surface part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-coated cemented carbide having excellent wear resistance and toughness, and a tool requiring wear resistance, impact resistance and thermal shock resistance, especially intermittent turning of steel. The present invention relates to a tough surface-coated cemented carbide that exhibits excellent fracture resistance when used as a tool or a milling cutting tool.

[0002]

2. Description of the Related Art Surface-coated cemented carbide has been practically used as a cutting tool, and the cutting tool is required to have both improved wear resistance of a coating film and improved toughness of a cemented carbide substrate. ing. Among the cutting tools, it is important to improve the toughness of the cemented carbide substrate particularly in the case of steel intermittent turning tools or milling cutting tools.

As one measure for improving the substrate of the surface-coated cemented carbide, in the substrate WC-cubic compound-Co-based cemented carbide, the amount of the cubic compound in the surface portion is smaller than that in other portions. Or a surface-coated cemented carbide with improved toughness, that is, fracture resistance has been proposed by providing a binder phase-enriched layer in which the binder phase concentration in the surface portion is increased as compared with other portions. . Typical examples of these are Japanese Patent Publication No. 57-39301 and Japanese Patent Laid-Open No. 62-1.
05628, JP-A-63-93865, JP-A-63-114970, and JP-A-63-1693.
56 and JP-A-1-287245. On the other hand, focusing on the crystal structure of tungsten carbide contained in the cemented carbide, plate-shaped tungsten carbide (hereinafter,
(Hereinafter referred to as “plate-like crystal WC”) to improve the properties of the cemented carbide, a typical one is as follows.
29484, JP-B-47-23049, JP-B-47-23050, JP-A-2-47239, JP-A-2-51408, JP-A-2-138.
434, JP-A-2-274827 and JP-A-5-339659.

[0004]

Among the prior arts in which the surface portion of the surface-coated cemented carbide substrate is modified, Japanese Patent Publication No. 57-39.
No. 301 discloses that the cubic crystal compound in the surface portion of the cemented carbide substrate is made smaller than in other portions. Further, JP-A-62-105628, JP-A-63-93865, JP-A-63-114970, JP-A-63-169356, and JP-A-1.
JP-A-287245 describes that the binder phase in the surface portion of the base body of the cemented carbide is poorer than other portions, or that the binder phase is poor and the cubic compound is also poor. These prior art cemented carbides with modified surface areas of the substrate have improved fracture resistance due to the effect of improving the toughness in the vicinity of the surface of the substrate, but since the hardness decreases, the resistance to plastic deformation There is a problem that the wear resistance is significantly deteriorated.

On the other hand, Japanese Patent Publication No. 46-29484, Japanese Patent Publication No. 47-23049, and Japanese Patent Publication No. 47-23, which are prior arts regarding a cemented carbide containing plate crystal WC.
No. 050, No. 2-47239, No. 2
-51408, JP-A-2-138434,
JP-A-2-274827 and JP-A-5-339.
Japanese Patent No. 659 describes a method for producing a cemented carbide containing plate-like crystals WC or a cemented carbide thereof. The method for producing a cemented carbide related to these plate-like crystals WC or the cemented carbide thereof is very difficult to produce the plate-like crystals WC, and the production method in which the production ratio of the plate-like crystals WC is small. Since it is a cemented carbide with a small content of plate-like crystals WC, or it is difficult to orient the plate-like crystals WC on the surface part of the cemented carbide, these are treated as surface-coated cemented carbide. Even if it is applied to the surface portion of the substrate, there is a problem that the effect of improving the toughness near the surface of the substrate is weak.

The present invention has solved the above-mentioned problems. Specifically, the surface portion of the cemented carbide is made to contain no cubic compound or is made poor, and A large amount of plate-like crystals WC in the part,
By coating a film on a substrate with the crystal planes of orientated in a specific direction, the hardness, toughness, plastic deformation resistance, impact resistance, and thermal shock resistance of the substrate surface are improved, and at the same time, an excellent film is obtained. The characteristics such as adhesion and abrasion resistance were able to be exhibited to the maximum extent, and as a synergistic effect between a substrate having a surface phase containing plate-like crystals WC and a film coated thereon. It is intended to provide a surface-coated cemented carbide having excellent wear resistance and fracture resistance.

[0007]

The present inventors have been studying for many years about a substrate in a surface-coated cemented carbide in which a film is coated on a substrate in which a cubic compound in the surface portion of the cemented carbide is impaired. When conducting a study to improve the hardness and toughness of the surface portion at the same time, the inclusion of the plate-like crystal WC in the surface portion tends to achieve the purpose, and further, the crystal plane of the plate-like crystal WC The present invention has been completed based on the knowledge that the characteristics of the coating film and the substrate can be further improved by aligning the orientations.

The toughness surface-coated cemented carbide of the present invention comprises Co
A cubic phase composed of 4 to 12% by weight of a binder phase containing as a main component, and a carbide, carbonitride, carbonate, or carbonitride oxide of W element and at least one of the elements of groups 4a and 5a of the periodic table. A coated cemented carbide obtained by coating a coating on a cemented carbide substrate comprising the first hard phase of a crystalline compound in an amount of 5 to 30% by weight and the balance being a second hard phase of tungsten carbide and inevitable impurities. , The surface portion at a depth of 5 to 30 μm from the surface of the cemented carbide to the inside does not contain the first hard phase, or the first hard phase has a greater hardness than the central portion of the cemented carbide. The second hard phase, which is poor and in the surface portion, is characterized by containing plate-oriented tungsten carbide in which crystals are oriented.

Specifically, the binder phase contained in the substrate in the surface-coated cemented carbide of the present invention is, for example, only Co, or 50% by weight or more of the binder phase is Co,
The case where the remainder is a Co alloy in which one or more of W, Cr, Mo, V, and Ni are solid-solved can be mentioned. Of these, C containing 10% by weight or less of W, Cr, and Ni as a solid solution
The binder phase made of o alloy is preferable because it can improve the corrosion resistance and the plastic deformation resistance. If the amount of this binder phase is less than 4% by weight with respect to the entire cemented carbide, the toughness deteriorates, and if it is used as a tool for surface-coated cemented carbide, the fracture resistance deteriorates, and conversely, it exceeds 12% by weight. If the amount increases, the hardness decreases and the wear resistance deteriorates.
It is defined as 2% by weight.

The hard phase contained in the substrate in the surface-coated cemented carbide of the present invention is composed of a first hard phase having a cubic crystal structure and a second hard phase of tungsten carbide. When the first hard phase is specifically exemplified,
(WTi) C, (WTi) (CN), (WTi) (C
O), (WTi) (CNO), (WZr) (CN),
(WTa) (CN), (WTiTa) (CN), (WN
b) (CN), (WTiZr) (CN) and the like. It is particularly preferable that the first hard phase is composed of carbonitride, carbon oxide, or carbonitride oxide because of the ease of production. If this first hard phase is less than 5% by weight with respect to the entire substrate, the plastic deformation resistance inside the substrate decreases and the wear resistance as a surface-coated cemented carbide tool deteriorates. If the amount exceeds the above range, the toughness is lowered and the fracture resistance is deteriorated, so the content is set to 5 to 30% by weight.

Specifically, the surface portion of the substrate in the surface-coated cemented carbide of the present invention does not contain the first hard phase which is substantially a cubic compound, but the second hard phase which is tungsten carbide. Oriented WC composed of and bonded phase
In the case of the example 1 containing, the content of the first hard phase is decreased or gradually decreased from the surface to the central part with respect to the central part of the substrate, and the rest is composed of the second hard phase and the binder phase, and is oriented. In the case of Example 2 containing the formed plate-like crystals WC, the average binder phase in the interior has a structure as in Example 1 and the average binder phase amount in the surface portion is 0.5 mm or more from the surface. For quantity,
In the case of Example 3, which is 1.05 to 1.30 times larger, Example 2
Example 4 in which the average binder phase amount in the surface portion is 1.05 to 1.30 times larger than the average binder phase amount in the depth of 0.5 mm or more from the surface. The case of can be illustrated. When the binder phase in the surface phase is non-uniformly distributed, for example, the binder phase content is higher in the surface and has the maximum value in the surface or the surface portion, or from the surface to the center portion. The case where the amount of the binder phase is gradually reduced can be exemplified as being preferable. If the depth of this surface portion is less than 5 μm from the surface, the toughness improvement due to the formation of the surface portion is small, and the effect of improving the fracture resistance as a surface-coated cemented carbide tool is low.
When the depth is more than μm, the plastic deformation resistance is deteriorated and the wear resistance is deteriorated. Therefore, the depth is set to 5 to 30 μm, and the surface depth of 10 to 20 μm is particularly preferable.

Further, the plate-like crystal WC contained in the surface portion of the substrate
Is a crystal orientation of which is oriented in a specific direction. Specifically, in a surface portion existing in at least one surface of a substrate having a polyhedral shape, a plane parallel to this surface is defined as a p-plane, and The vertical cross section is taken as the h-plane, and the peak intensities measured by the X-ray diffraction method on the (001) plane and the (101) plane of the WC crystal on the p-plane and the h-plane are p (001), p
When expressed as (101), h (001) and h (101), p (001) / p (101)> 1.2 × h (0
01) / h (101) is preferable. p (00
1) / p (101) ≦ 1.2 × h (001) / h (10
In 1), the effect of orienting the plate-like crystals WC was low, and the effect of improving the hardness and toughness of the substrate was small, and p (001) / p (1
It is more preferable that 01)> 1.5 × h (001) / h (101).

Further, a plate crystal W contained in the surface portion of the substrate
C has an aspect ratio of 3 observed on the cross-sectional structure of the substrate.
It is preferably 20 to 20 and is 30% by volume or more of the whole tungsten carbide contained in the surface portion, and particularly preferably 50% by volume or more of the whole tungsten carbide contained in the surface portion.

On the other hand, the binder phase constituting the surface portion of the substrate is
The average binder phase amount in the surface portion is 1.05 to 1.30 from the internal average binder phase amount at a depth of 0.5 mm or more from the surface of the substrate.
When the amount is twice, the toughness of the surface portion of the substrate is increased and the fracture resistance of the surface-coated cemented carbide tool can be further improved, which is preferable.

The surface portion of the substrate is reduced in comparison with the content of the second hard phase made of tungsten carbide containing platy crystal WC and the binder phase, or in addition to these, the content of the central portion of the substrate. The first hard phase consisting of a cubic compound may be present, but the former is preferred for applications that emphasize fracture resistance, and the latter for applications that emphasize wear resistance and heat resistance at high temperatures. The optimum surface-coated cemented carbide can be obtained by adjusting the plate crystal WC content, the binder phase content, and the first hard phase content according to the application and shape.

When these surface-coated cemented carbides of the present invention are used as cutting tool tips having a polyhedral shape, it is possible to obtain a surface-coated cemented carbide tool if at least the rake face of the cutting tool tip has a surface portion. It is preferable since the fracture resistance can be further improved.

The coating film coated on the substrate having the surface portion having the above-mentioned structure may have the film quality of the coating film conventionally coated on the surface of the cemented carbide and the film structure of the coating film. Specifically, this coating is, for example, a compound containing at least one metal element of the 4a, 5a, and 6a groups of the periodic table,
Aluminum oxide, hard boron nitride, cubic boron nitride, diamond-like carbon and diamond can be mentioned. Among these coatings, titanium carbide, titanium nitride, titanium carbonitride, titanium carbonate, titanium oxynitride, titanium oxycarbonitride, titanium nitride / aluminum, titanium carbonitride / aluminum, titanium oxynitride / aluminum, oxycarbonitride It is preferable that the substrate is coated with a hard coating composed of a single layer of titanium / aluminum or aluminum oxide or a multilayer of two or more types. The composition of these coatings is such that when coating these coatings directly on the substrate,
It is also preferable to interpose other coatings on the substrate and to coat these coatings thereon, or to adopt such a coating constitution and then further coat another kind of coating. It is preferable that the total thickness of the coating in these various coating configurations is 2 to 20 μm in order to maximize the effect of the coating.

As for the constitution of this coating, specifically, for example, the coating constitution of sequentially coating from the surface of the substrate is TiN-TiC-
_{TiN, TiCN-TiC-Al 2} O 3 -TiN, TiN
_{-TiCN-TiC-Al 2 O 3} -TiN, TiC-Ti
_{CN-Al 2 O 3 -TiN,} TiCN- (TiAl) N,
Such _{TiCN- (TiAl) N-Al 2} O 3 -TiN double layer can be mentioned. The total thickness of this coating is 2 μm
If it is less than 20 μm, the wear resistance is not improved by the coating, and conversely it is 20 μm.
If the thickness exceeds m, the strength is reduced due to the brittle coating and the fracture resistance is deteriorated, so the thickness is set to 2 to 20 μm. In particular, the total thickness of the coating is 8 to 1 for turning tools.
It is preferably 5 μm and 3 to 6 μm for milling tools.

In the toughness surface-coated cemented carbide of the present invention, a cemented carbide which is a substrate is prepared by the following procedure, and the chemical vapor deposition method ( CVD method) or physical vapor deposition method (PVD method),
Alternatively, it can be manufactured by adjusting various coating materials and film thicknesses by both methods.

The cemented carbide as the substrate may be prepared by various methods, but as a simple method, specifically, for example, W, Co, W--Co alloy, an alloy containing W and Co, W-Co-C composite carbide, a starting material in which a predetermined amount of a carbon source material necessary for forming carbon, graphite or carbide is contained in a W- and Co-containing material that is one or more kinds of W-Co-C composite carbide. In addition, WC, Co, Ni, Cr, which have been commercially available so far to obtain the desired cemented carbide composition,
V, TiC, TiN, TiCN, TaC, (TiW)
Various starting materials such as C and (TiTaW) C can be manufactured through the conventional powder metallurgical methods of mixing, molding, and sintering.

[0021]

The toughness surface-coated cemented carbide of the present invention has a plate-shaped crystal W in the surface portion formed on the surface of the cemented carbide substrate.
By containing C and having the plate-like crystals WC oriented in a specific plane, the plate-like crystals WC have the effect of significantly increasing the hardness, toughness, and strength on that plane, and The coating on the substrate has a function of enhancing wear resistance, and synergies between the structure of the surface of the substrate and the coating on the substrate.
By virtue of the effect, it has the effect of remarkably improving the wear resistance and fracture resistance when the coated cemented carbide is used as a cutting tool.

[0022]

Example 1 Commercially available W having an average particle diameter of 2.2 μm, 1.0 μm of Co, 6 μm of graphite (denoted as G in the table), 3.5 μm of WC, 1.0 μm of (WTi). C composite carbide (weight ratio WC: TiC = 70: 30),
1.0 μm TaC, 1.5 μm NbC, 1.2 μm
Each of the powders of TiN and 0.02 μm of TiO ₂ was weighed according to the compounding composition shown in Table 1 and inserted into a stainless steel pot together with an acetone solvent and a cemented carbide ball.
After time pulverization and mixing, it was dried to obtain a mixed powder. Using this powder, SNGN1204 described in JIS-B4120
It is press-molded with a die for 08 shape at a pressure of ² ton / cm ² , and the obtained powder compact is subjected to an atmospheric pressure of 10 Pa.
By heating and sintering at 1420 ° C. for 1 hour in a vacuum, substrates 1 to 5 of cemented carbide for obtaining the product of the present invention and substrates 1 to 5 for obtaining the comparative product were obtained.

The various substrates thus obtained were cut in the direction perpendicular to the upper and lower surfaces (the surface perpendicular to the pressing direction), the cut surfaces were subjected to polishing and lapping with 1 μm diamond paste, and then the cross section had a texture. Observation, composition analysis, and X-ray diffraction were performed. For these various substrates,
Thickness of the surface portion (depth from the surface), average composition in the surface portion and within 0.5 mm from the surface (equivalent to the center portion), WC average particle diameter in the surface portion, and plate crystals in the surface portion The percentage of WC was determined and these results are shown in Table 2.

Next, after polishing the upper surface or lower surface of each of the various substrates by lapping with diamond paste for about 3 μm, the micro Vickers hardness of the surface portion,
Micro Vickers hardness within 0.5 mm from the surface, fracture toughness value K _1C near the surface including the surface part (load by IM method:
196 N), the peak intensity ratio of the (001) plane to the (101) plane of the WC crystal in the surface portion was determined, and these results are shown in Table 3.

[0025]

Example 2 As shown in Table 1 of Example 1,
Using the mixed powders obtained by treating the compounding compositions of 2, 3 and 1, 2, 3 for the comparative products in the same manner as in Example 1, JI
Using a die of CNMG120408 (with a breaker) described in S-B4120, press forming and sintering were performed under the same conditions as in Example 1 to obtain a cemented carbide chip for a cutting tool.
After grinding the upper and lower boss surfaces of these chips and performing R honing of 0.03 mm with a diamond brush on the edge of the chip, a CVD coating device was used to obtain a film thickness of 1.0 μm from the substrate side of the chip. TiN,
6.0 μm TiCN, 1.0 μm TiC, 3.0 μm
m of Al ₂ O ₃ and 1.0 μm of TiN were sequentially coated, and a total thickness of 12 μm was coated to obtain the present invention products 6, 7, 8 and comparative products 6, 7, 8. . Using the surface-coated cemented carbide tool tip thus obtained, the work material: S
48C (with 4 grooves), cutting speed: 200m / min,
A dry interrupted turning test was conducted under the conditions of depth of cut: 2.0 mm, feed: 0.25 mm / rev, and the life time until the chipping of the cutting edge, the damage of the cutting edge or the average flank wear width was 0.35 mm was obtained. As a result, the product of the present invention 6 = 35 min,
Inventive product 7 = 47 min, Inventive product 8 = 30 min, Comparative product 6 = 17 min, Comparative product 7 = 27 min, Comparative product 8
= 19 min, each reached the end of life.

[0026]

[Example 3] 4, which is shown in Table 1 of Example 1, for the product of the present invention
SEKR described in JIS-B4120 was carried out in the same manner as in Example 2 using the compounding compositions of 5 and 4 and 5 for comparative products.
A cemented carbide chip of 1203AFTN (with breaker) was obtained. After grinding the lower boss surface of these chips and performing R honing of 0.03 mm with a diamond brush on the blade edge, a CVD coating device was used to obtain a film thickness of 1.0 μm from the substrate side of the chip. TiN,
1.0 μm TiCN, 0.5 μm Al ₂ O ₃ , 0.5
The coatings made of TiN having a thickness of 3 μm are sequentially coated to cover the total coating thickness of 3 μm.
0 was obtained. Using each of the three surface-coated cemented carbide tool tips thus obtained, the work material: SCM440, cutting speed: 100 m / min, depth of cut: 2.0 mm, feed:
A dry milling cutting test was performed under the condition of 0.25 mm / blade, and the average life time until chipping or breakage of the cutting edge was obtained. As a result, the product of the present invention 9 = 27 min, the product of the present invention 10 =
35 min, comparative product 9 = 19 min, comparative product 10 = 21
It reached the end of life at each min.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

The toughness surface-coated cemented carbide of the present invention does not contain the cubic compound which is the first hard phase, but has a surface portion having a WC-Co structure-WC-cubic compound-
Compared to a conventional surface-coated cemented carbide obtained by coating a hard film on a Co-based cemented carbide or a surface-coated cemented carbide deviating from the present invention having a surface portion containing a small amount of plate-like crystals WC, turning with high intermittent interruptions There is an excellent effect that chipping and chipping hardly occur in processing and milling and that the life is remarkably long.

Claims (6)

[Claims] 1. A carbide, carbonitride, carbonate, or charcoal of 4 to 12% by weight of a binder phase containing Co as a main component and W element and at least one element of 4a and 5a elements of the periodic table. 5-30% by weight of the first hard phase of the cubic compound composed of nitric oxide
And a coated cemented carbide obtained by coating a coating on a cemented carbide substrate having the second hard phase of tungsten carbide and unavoidable impurities, the remaining amount being 5 to 30 μm from the surface of the cemented carbide to the inside. The surface portion at a depth does not contain the first hard phase, or the first hard phase is poor as compared to the center portion of the cemented carbide, and the second portion in the surface portion is A tough surface-coated cemented carbide characterized in that the hard phase contains plate-oriented tungsten carbide in which crystals are oriented. 2. The coating comprises titanium carbide, titanium nitride,
Titanium carbonitride, titanium carbonate, titanium oxynitride, titanium oxycarbonitride, titanium nitride / aluminum, titanium carbonitride / aluminum, titanium oxynitride / aluminum, titanium oxycarbonitride / aluminum, aluminum oxide 2. A toughness surface-coated cemented carbide according to claim 1, wherein the hard coating comprises a layer or a multi-layered hard coating of two or more kinds, and the total thickness of the coating is 2 to 20 [mu] m. 3. The plate-shaped tungsten carbide contained in the surface portion has an aspect ratio of 3 to 20 observed on the sectional structure of the substrate, and the entire tungsten carbide contained in the surface portion. 30% by volume or more of the cemented carbide with a tough surface-coated cemented carbide according to claim 1 or 2. 4. The cemented carbide substrate has a polyhedral shape, and the surface portion of at least one surface of the polyhedral shape has a plane parallel to the surface as a p-plane, and a cross section perpendicular to the surface is h. Planes, and the peak intensities measured by the X-ray diffraction method on the (001) plane and the (101) plane of the tungsten carbide crystal on the p plane and the h plane are p (001) and p (1
01), h (001) and h (101), p (001) / p (101)> 1.2 × h (00
1) / h (101)
The tough surface-coated cemented carbide according to 2 or 3. 5. The cemented carbide substrate is a cutting tool tip having a polyhedral shape, and the surface portion is formed on a rake face, 1, 2, 3 or 4.
A toughened surface-coated cemented carbide as described. 6. The average amount of the binder phase contained in the surface portion is 1.05 to 1.30 times larger than the average amount of the binder phase in the depth of 0.5 mm or more from the surface. The tough surface-coated cemented carbide according to claim 1, 2, 3, 4 or 5.